The invention relates to a sensor arrangement which includes a layer of light-sensitive and/or X-ray sensitive sensors which are arranged in a distributed fashion.
Sensor arrangements provided with two-dimensional, large-area layers of light-sensitive and/or X-ray sensitive sensors are used notably for the dynamic reproduction of X-ray images in the medical field. Large-area X-ray sensors of this kind are also referred to as “flat dynamic X-ray detectors” (FDXD). FDXD-like detectors are universal detector components which can be used in a variety of application-specific X-ray apparatus. The applications include not in the least the computed tomography and nuclear medicine.
An FDXD X-ray detector is known, for example, from EP 0 440 282 B1. This known X-ray detector is based on thin-film technology in which an electrical circuit is formed by deposition of thin layers on a substrate. In conformity with EP 0 440 282 B1 there is formed a matrix arrangement which consists of photodiodes which briefly conduct an electric current, because of the absorption of photons, and thin-film transistors which enable selective coupling of the respective photodiode to read-out leads. Amorphous silicon is used as the semiconductor material. The arrangement thus obtained constitutes a large-area photosensor which can be rendered sensitive to X-rays by depositing an additional scintillator layer on the light-sensitive photodiodes. The scintillator layer then absorbs X-ray quanta and converts such quanta into light quanta which can be detected by the photodiodes.
Also known are arrangements which convert X-rays directly into electric signals. For example, DE 40 02 429 A1 describes a sensor matrix which is manufactured by means of the thin-film technology and in which storage capacitances on a thin-film plate are used instead of photodiodes and a directly converting material is used instead of the scintillator layer.
In all known FDXD-like sensors, integrated circuits such as, for example, CMOS circuits, are connected at the edge of the large-area thin-film electronics, said circuits serving for the row-wise driving of the matrix cells and for the column-wise amplification and acquisition of the signals from the matrix cells. It is a drawback that the so-called “switching noise” during the row-wise reading out of the matrix and the long connection leads between the individual sensors and the circuits give rise to a comparatively high noise level.